Fracking is an oil-extraction technique in which millions of gallons of water, mixed with sand and chemicals, are injected underground at high pressure. That cracks the rocks, letting the oil out. Around the country, hydraulic fracturing has led to record levels of oil and gas production.

While fracking has been big news for a while in Pennsylvania, North Dakota and elsewhere in the country, it has yet to become a popular topic of dinner conversation in California. That’s likely going to change.

Why? Because the federal Bureau of Land Management has opened up 18,000 acres in Monterey, Fresno and San Benito Counties to oil leases. But the oil deep in what’s called the Monterey Shale is notoriously tough to extract. “Most if it is locked inside the shale rock,” Lauren Sommer reports. “But recently, oil companies have gotten a lot better at getting oil out of shale thanks to hydraulic fracturing.”

California’s Division of Oil, Gas and Geothermal Resources (DOGGR) is now drafting regulations around fracking. But many environmentalists are just dead-set against the technique, worrying about water contamination and other negative effects. So let’s hear what former Vice President Al Gore — one of the world’s most influential advocates on climate change and other environmental issues — has to say.

Forum host Michael Krasny: What do you think about the anticipated fracking expansion in California?

Al Gore: I’m concerned about it. It has pluses and minuses. Advocates have long pointed out that natural gas has only 50 percent of the CO2 content when it’s burned compared to coal. But a lot of it leaks in the fracking process. And when the methane leaks into the atmosphere, each molecule has 70 times the potential warming effect compared to CO2 over a 10-20 year period, and then it lessens somewhat. But that means not very much needs to leak to wipe out the advantage.

And then there are the water requirements. Six million gallons on average for each new fracking well. And the water that’s used is mixed with very toxic chemicals, and that sometimes pollutes the groundwater. The industry claims it doesn’t, but there are too many examples that shows that it does — often when they re-inject the poisoned fracking water back deep into the earth.

These and other issues are ones that I think are deserving of careful exploration.

People often say fracking is an issue that requires the classic question: is the glass half-full or half-empty?

Well, the Earth’s atmosphere is completely full. And we’re going to have to make a shift to renewable energy sources. We have the ability to do that. The report came out recently that last year the largest new additions to electricity production in the U.S. came from wind — 42 percent of all new energy production from wind. In Australia, wind energy, a report says, is now cheaper than electricity from a new coal plant or a new gas plant. And solar photovoltaic energy is spreading far more rapidly than anyone thought was possible. In 2010 the world’s cumulative investments in renewable energy for the first time exceeded the world’s investments in fossil fuel energy.

Now the fracking wave over the last two years has put [non-renewables] out in front again, but it is inexorable that we will shift to renewable energy. Part of the problem with speeding up this transition, though, is that we provide massive subsidies to coal and oil, and on a global basis it amounts to about $500 billion a year. We ought to save money buy stopping those subsidies to the dirty carbon fuels.

I asked Lauren Sommer to comment on one part of what Gore said: his contention that there have been “too many examples” of groundwater being contaminated by the fracking process.

“Groundwater contamination has been one of the most controversial questions in the fracking debate,” Sommer says. “While there have been documented cases of methane seeping into groundwater, linking it directly to fracking activity has been trickier. The EPA is still investigating one of the most high- profile cases in Pavillion, Wyo., where early results showed that fracking chemicals could be seeping into the groundwater there.”

New research has concluded that salty, mineral-rich fluids deep beneath Pennsylvania’s natural gas fields are likely seeping upward thousands of feet into drinking water supplies.

Though the fluids were natural and not the byproduct of drilling or hydraulic fracturing, the finding further stokes the red-hot controversy over fracking in the Marcellus Shale, suggesting that drilling waste and chemicals could migrate in ways previously thought to be impossible…

The study, conducted by scientists at Duke University and California State Polytechnic University at Pomona and released today in the Proceedings of the National Academy of Sciences, tested drinking water wells and aquifers across Northeastern Pennsylvania. Researchers found that, in some cases, the water had mixed with brine that closely matched brine thought to be from the Marcellus Shale or areas close to it.

No drilling chemicals were detected in the water, and there was no correlation between where the natural brine was detected and where drilling takes place.

Still, the brine’s presence – and the finding that it moved over thousands of vertical feet — contradicts the oft-repeated notion that deeply buried rock layers will always seal in material injected underground through drilling, mining, or underground disposal. Full article

Meanwhile, says KQED Science Senior Editor Craig Miller, the problem with fracking may have less to do with the specific process and more with the fact that it’s enabled more drilling in general …

While the term “fracking” makes for great poster plays at demonstrations, it’s just one phase of a well’s development,” he says. “The biggest threat to water quality may be simply the enormous new boom in drilling that fracking techniques (and horizontal drilling) have enabled. Thousands of new wells (and more reworked old wells) mean a lot more “straws” being stuck through underground rock formations. Each of those straws represents a chance that somebody might cut corners on making sure the well is properly sealed off from the surrounding aquifer. It’s the reason that regulators keep harping on ‘well casing management.’

Fracking comes with its own concerns, of course, like seismic risk, air pollution from arrays of diesel generators, and the disposal of huge quantities of waste water back into the ground.